1. Field of the Invention
The present invention relates to a method and apparatus for abatement of effluent from any CVD process using a source reagent having a metal organic loosely bound to an organic or organometallic molecule such that upon exposure to heat such bond is readily cleavable e.g., abatement of effluents from processes involving the deposition of copper on a substrate by chemical vapor deposition (CVD).
2. Description of the Related Art
Copper deposition has become one of the most important and rapidly growing areas in integrated circuit manufacturing. Deposition of copper can be accomplished by various techniques, with chemical vapor deposition (CVD) becoming progressively more widespread.
The precursors used in copper CVD, however, are relatively new and limited information has been published on their abatement. One of the major chemistries currently being employed for CuCVD utilizes Cu(hfac)TMVS as a copper source reagent. This precursor, Cu(hfac)TMVS, wherein hfac=1,1,1,5,5,5-hexafluoroacetylacetonato and TMVS is trimethyl vinyl silane, CH2=CHxe2x80x94Si(CH3)3, is commercially available from Schumacher Division of Air Products and Chemicals, Inc. (Allentown, Pa.) under the trademark CupraSelect. In the CupraSelect(trademark) process, the generally accepted mechanism for the deposition of copper from the Cu(hfac)TMVS precursor by CVD involves the liberation of TMVS on the wafer surface and its intact desorption. This is followed by collision and disproportionation of two Cu(I)(hfac) molecules, to yield Cu(0) (metal) and Cu(II)(hfac)2. Copper metal thereby is incorporated in the growing film, while Cu(II)(hfac)2 desorbs therefrom.
Under certain process conditions, Hhfac (CF3xe2x80x94COxe2x80x94CHxe2x95x90COHxe2x80x94CF3), the protonated, acidic form of hfac, is produced in the film formation process. This can occur as a result of the addition or presence of water. Alternatively, Hhfac can form in consequence of the use of H2 as a reducing gas in the CVD process.
Thus, in the use of Cu(hfac)TMVS as a copper source reagent for CVD, the reaction by-products of the copper deposition process include Hhfac, TMVS and Cu(II)(hfac)2. These reaction by-products are correspondingly present in the effluent from the copper CVD process when Cu(hfac)TMVS is employed as a copper source reagent, and require abatement in the treatment of the effluent gas from the process.
One of the major process challenges in the CupraSelect(trademark) process relates to the fact that the Cu(hfac)TMVS precursor tends to decompose in the hot environment of the dry vacuum pumps that are used in the process. This decomposition produces corresponding decomposition products that severely shorten vacuum pump life.
Schumacher has developed a technique for the abatement of waste gas species from the CupraSelect(trademark) process. In this abatement technique copper CVD species escaping the CVD process chamber are passed through a heated section of the vacuum line downstream from the CVD chamber, and upstream of the vacuum pump, so that the copper species are converted into volatile materials (Cu(hfac)2 and TMVS, with deposition of copper on the heated section internal surfaces). These volatile materials subsequently pass through the dry vacuum pumps without deposition and without attendant pump damage from deposited solids. The valuable hfac material is recovered downstream from the dry vacuum pump in a cold trap, which condenses the Cu(hfac)2 while allowing the TMVS to pass through. The valuable Cu(hfac)2 can then be collected and recycled to an upstream Cu(hfac)TMVS manufacturing operation.
The Schumacher technique is described in detail in xe2x80x9cSafety and environmental concerns of CVD copper precursors,xe2x80x9d B. Zorich and M. Majors, Solid State Technology;September 1998, pp. 101-106.
Despite its utility, the Schumacher efficient abatement technique suffers from a number of deficiencies.
One major deficiency relates to the fact that there is a significant amount of Cu(hfac)TMVS and Cu(hfac)2 passing through the process system, which can result in excessive copper emissions in the discharge vent gas.
Another deficiency of the Schumacher technique relates to the fact that significant amounts of free TMVS pass through the process system. TMVS is highly flammable, having a flashpoint of xe2x88x9219xc2x0 C., and a lower explosive limit (LEL) of 0.5% in air.
A further deficiency of the Schumacher technique relates to the fact that the cold trap is not very efficient for removing Cu(hfac)2. The cold trap also presents significant operational difficulties, since the cold trap must be removed and separately processed in order to recover Cu(hfac)2.
The semiconductor manufacturing industry, and other industrial operations that utilize CupraSelect(trademark) reagents for formation of copper on substrates, would therefore be greatly benefited by a process that overcomes the aforementioned disadvantages.
The foregoing issues are not unique to the CupraSelect(trademark) process or other copper metallization processes using other Cu CVD precursors, such as Cu(hfac)-R where R is any of a series of organic or organometallic molecules. Some examples include Cu(hfacac)-3-hexyne, (C5HF6O2)Cuxc2x7(C6H10), and Cu CVD precursors containing organo moieties such as 3-hexyne (CH3xe2x80x94CH2xe2x80x94Cxe2x89xa1Cxe2x80x94CH2xe2x80x94CH3), dimethylcyclooctadecene (DMCOD) and 3-methylhex-ene-yne (3MHY). These issues also apply to other CVD processes which use a source reagent having a metal organic loosely bound to a organic or organometallic molecule such that upon exposure to heat such bond is readily cleavable.
The present invention relates to a method and apparatus for abatement of effluent from any CVD process using a precursor (source reagent) having a metal organic loosely bound to a organic or organometallic molecule such that upon exposure to heat such bond is readily cleavable. More particularly, the present invention relates to a method and apparatus for abatement of effluent from a process for depositing copper on a substrate from an organocopper source reagent.
In one aspect, the invention relates to a method wherein the effluent from the CVD process is contacted with a sorbent having sorptive affinity for the organometallic source reagent, as well as for byproduct species deriving from the deposition process utilizing such source reagent.
The sorbent may comprise a physical sorbent and/or a chemisorbent, as desired to effect desired abatement of effluent species.
A pump may be disposed upstream of the sorbent, and arranged to maintain predetermined pressure conditions in the upstream deposition process, with (1) a pre-pump heating device operative to at least partially convert organocopper species in the effluent to conversion products that are less susceptible to deposition in the pump, and/or (2) a post-pump cold trap operative to remove condensable and/or solidifiable components from the effluent.
The above-described method may further comprise monitoring the effluent discharged from the sorbent contacting step, to detect breakthrough of a selected component, e.g., by a quartz microbalance detector.
The invention in another aspect relates to an apparatus for abatement of effluent from a CVD process using an organometallic source reagent, such apparatus comprising:
a sorbent bed having sorptive affinity for the source reagent and byproduct species deriving from the source reagent; and
a flow path joining the process in gas flow communication with the sorbent bed so that effluent is flowed through the sorbent bed, to at least partially remove source reagent and deposition byproduct species from the effluent.
A pump may be disposed upstream of the sorbent, and arranged to maintain predetermined pressure conditions in the upstream deposition process, with (1) a pre-pump heating device operative to at least partially convert organocopper species in the effluent to conversion products that are less susceptible to deposition in the pump, and/or (2) a post-pump cold trap operative to remove condensable and/or solidifiable components from the effluent.
The apparatus may further comprise an endpoint sensor operatively arranged to sense breakthrough of one or more effluent components in effluent from the sorbent bed.
The apparatus may further include a semiconductor manufacturing facility in which copper is deposited on a substrate, e.g., by a CVD process.
Other aspects and features of the invention will be more fully apparent from the ensuing disclosure and appended claims.